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面向Massive MIMO的波束赋形算法研究及实现
Thesis Advisor尹志刚
Degree Grantor中国科学院研究生院
Place of Conferral北京
KeywordMassive Mimo 天线子阵列 数字波束赋形 混合波束赋形 专用代数指令提取
AbstractMassive MIMO关键技术由于能够提供更高的信道自由度,通过空间域的扩展提高系统的频谱及能量效率,成为5G关键技术研究重点。但是,Massive MIMO关键技术通常在基站侧需要部署数十根乃至上百根天线,导致基站侧发送信号在波束赋形处理过程中的运算复杂度大幅度增加,因此极大地制约了Massive MIMO关键技术在5G通信系统中的实际应用。同时,Massive MIMO关键技术还面临由于天线个数的增加,而造成的高成本问题。在这样的背景之下,本论文通过设计低复杂度、低成本的波束赋形算法用以解决Massive MIMO关键技术的应用瓶颈。除此外,本论文根据所设计的Massive MIMO波束赋形算法,提取波束赋形算法面向UCP处理器的专用代数指令,从而进一步从波束赋形算法实现角度攻克Massive MIMO的工程应用壁垒。
本论文通过引入天线子阵列的Massive MIMO通信系统结构,重新构造波束赋形权值矩阵,将此前复杂的求取波束赋形矩阵以获取最大接收功率的过程,转化为求取相独立的不同天线子阵列的最优波束赋形列向量。此外,本论文采用幂代法,代替此前复杂度高且难并行化的SVD算法。复杂度分析及仿真结果表明,本论文提出的数字波束赋形算法,相较于传统的SVD算法而言,运算量降低至少一半以上。同时,随着迭代次数增加,本论文提出的波束赋形算法在获取更高增益的同时不会大幅增加运算复杂度。
Other AbstractDue to the Massive MIMO technology is able to provide higher channel freedom and improve the spectrum efficiency, it has been paid more and more attentions. However, the Massive MIMO teconology, requiring dozens or even hundreds of antennas at the base station, produces significant increase in computational complexity in the signal process of beamforming procedure, which has greatly restricted the Massive MIMO development in the practical application of 5G systems. In addition, the Massive MIMO technology is confronted with the increase in the number of antennas, resulting in high cost preoblems. Under these backfrounds, the paper aims to solve the bottleneck of Massive MIMO technology by designing low-complexity and low-cost beamforming algorithm. In addition, this paper designs the parallelization based on the UCP processor characteristics and instruction sets to overcome the engineering application barrier of Massive MIMO teconology.
According to the system based on the sub-array structure, this paper, by reconstructing the beamforming matrix, decomposes the process of obtaining the beamforming matrix to get the maxiumum received power into a series of ones much easier to be solved by optimizing each antenna array one by one. In order to get the beamforming vector of each sub-array with fewer computational complexity, this paper proposes to utilize the power iteration algorithm to replace the high-complexity SVD altorithm with difficulty of parallelism. According to the detailed complexity analisis and simulation results, compared with the traditional SVD beamforming algorithm, the complexity of the proposed digital beamforming algorithm based sub-array structure is reduced by at least half. Meanwhile, with the increase of the number of iterations, the digital beamforming algorithm proposed in this paper could obtain necessary performance gain without significantly increasing the computational complexity.
In order to solve the high-cost problem caused by the digital beamforming algorithm, this paper introduces the analog beamforming on the basis of the proposed digital beamforming. In this paper, the digital beamforming adjusts the results made by analog beamforming to minimize the mean square error between the hybrid beamforming algorithm and the proposed digital beamforming. It is showed the proposed hybrid beamforming algorithm, which has the ability to obtain the near-optimal system performance, can reduce the hardware cost, and inherit the low-complexity advantage of the proposed digital beamforming algorithm.
In order to optimize the pipeline efficiency and reduce the signal process delay, this paper extracts the main operator feature of these two altorithm, and designs the parallelization based on the UCP processor characteristics and instruction sets. Then this paper gives several pratical solutions to extract algebra instructions. According to the algrbra instructions cycles of different beamforming units, it is shown that the extracted beamforming algebra instructions based on UCP processor can support the requirements of 5G system to achieve the millisecond end-to end delay.
Document Type学位论文
Recommended Citation
GB/T 7714
王戈. 面向Massive MIMO的波束赋形算法研究及实现[D]. 北京. 中国科学院研究生院,2017.
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